The resistance

What is the resistance of an aluminum wire, 0.2 km long and 10 mm in diameter?

Correct answer:

R =  0.0713 Ω

Step-by-step explanation:

l=0.2 km→ m=0.2⋅ 1000  m=200 m D=10 mm→ m=10:1000  m=0.01 m  r=D/2=0.01/2=2001​=0.005 m  S=π⋅ r2=3.1416⋅ 0.0052≐0.0001 m2 ρ=2.8⋅ 10−8=2.8⋅10−8 Ωm R=ρ⋅ l/S=2.8⋅10−8⋅ 200/0.0001=0.0713 Ω

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